Difference in Window Area between EnergyPlus and OpenStudio DOE Prototype Buildings
Hello, I used OpenStudio (v. 1.12) and ran the measure 'Create DOE Prototype Building' to create an ASHRAE 90.1-2010- SmallOffice building in climate zone 2A. The results are shown below:
Overall energy use:
End energy use:
I then proceeded to download and run the equivalent 90.1-2010 EnergyPlus model from the Commercial Prototype Building Models website in EnergyPlus version 8.5. The EnergyPlus results are shown below:
Although the overall results are fairly close (201.99 GJ vs 203.18 GJ is less than 1% difference in total site energy), it appears that the individual end use loads vary quite a bit. The cooling is 27% higher (41.71 GJ vs 30.33 GJ) in the EnergyPlus prototype and the lighting is 20% less (53.89 GJ vs 65 GJ) in the EnergyPlus prototype.
Since the cooling load increased and lighting decreased, my suspicion was that the WWR might be different between the two prototype buildings and it is.The southern WWR in the EnergyPlus prototype building is 24.44%, while the OpenStudio version is 19.81%. Why is there a difference between these models window-to-wall ratios? Are there any other differences between the prototype buildings that I should be wary of?
This looks like a bug in the OpenStudio implementation. I filed an issue. Thanks.
No problem! I will fool around a bit with the WWR of the south wall of the OpenStudio version and see if any other errors pop up.
It appears that the fault might be a difference in the the Southern Door between the EnergyPlus model and the OpenStudio model. The EnergyPlus prototype uses a 'glass door' while the OpenStudio prototype version uses a non-glass door (Typical Insulated Metal Door R-1.43). It appear this is the case for other SmallOffice buildings in other climate zones as well. I'm not sure if this was a conscious decision or which model would be a more accurate representative of an ASHRAE 90.1-2010 SmallOffice building. I'll see if other building types also have this same issue.
The OpenStudio models were/are intended to be replicas of the EnergyPlus models. This will be fixed. Thanks for identifying it.